Firefox 9 has been officially released.
The latest update to the popular browser brings several new features and
improvements, the biggest of which is a modification to the JavaScript
engine that provides a big performance boost of up to 30 percent in some
cases.The latest Firefox uses type inference,
a method of determining and setting the type of a JavaScript variable
at runtime which leads to less overhead and more efficiently used
memory. A more comprehensive explanation as well as some benchmark results are available here.

Mac OS X Lion users get better theme integration and support for
two-finger swipe. Firefox 9 also comes with plenty of improvements under
the hood including better support for web technologies such as HTML5,
MathML and CSS.